Total chlorine water detection system for medical fluid treatments

ABSTRACT

A system and method for determining a concentration of total chlorine in dialysis water are provided. The system comprises a main unit housing a KI/water sample chamber and a sodium sulfate chamber. A first electrode pair bridges the two chambers and generates tri-iodide proportional to the amount of total chlorine in the water sample. A second electrode pair in contact with fluid in the KI/water sample detects an amount of tri-iodide generated by the first electrode pair. The system is suitable for use in connection with, or for incorporation into, a water purification system for generating dialysis fluid, and may include a display that alerts the user to stop or prevent a hemodialysis treatment if the total chlorine level exceeds a predetermined level.

PRIORITY CLAIM

This application is a continuation of U.S. application Ser. No.13/797,066, filed Mar. 12, 2013, which claims priority to U.S.provisional patent application Ser. No. 61/716,966, filed on Oct. 22,2012, the entire contents of each of which are incorporated herein byreference and relied upon.

BACKGROUND

This application relates generally to water purity qualitative analysis,and in particular to water used for medical applications.

Water purity qualitative analysis determines the presence or absence andthe amounts of chemicals and their mixtures in water. Water purityqualitative analysis can require field kits for testing the waterfacilities. The field test kits are known in general to havedisadvantages including inaccuracies in data, false positives,limitations of single-factor testing, e.g., in measuring chlorine levelsin pools and spas, and overall accuracy. Disadvantages of fieldqualitative testing kits also include an inability to reproducestatistics. Outdoor and indoor conditions, such as humidity,temperature, wind, rain and noise add to the inherent disadvantages oftest kit qualitative field-type water monitoring.

Testing can alternatively be done by mixing water with powders in vials.Both strips and vials change the color of water to indicate if the waterpurity meets safe levels. Color change analysis leaves open thepossibility that the person viewing the change cannot see color well andthat multiple viewers may compare the water color to the test markersdifferently. Color viewing test results accordingly provide low tomoderate accuracy in measuring amounts of chlorine, bacteria and acidity(pH levels), which each affect water purity.

Sensors are used in municipal, industrial and residential water systemsto test variables affecting water purity for human consumption and use,as well as to monitor water purity for healthy ecosystems of otherliving organisms. Sensors measure temperature, pH levels anddesalination (salt control) compounds. However, using sensors inqualitative water purity field testing can result in drawbacks due tomoderate measurement accuracy for multiple types of water puritystatistics.

Using chemistry-based field-testing to gather qualitative water-puritydata gives incomplete statistical outcomes, similar to the pHcolorimetric qualitative testing. Operating at a neutral pH,chemistry-based testing, like colorimetric testing, measures particularaspects of inorganic substances in water, rather than all itscharacteristics. As an example, at neutral pH, both of thechemistry-based and colorimetric tests measure dissolved iron amounts,but not iron particles. In addition, ammonia levels from biologicaldecay compromise qualitative measurements using chemistry-based fieldtesting of nutrients in wastewater.

As discussed above, known water testing techniques have multipledrawbacks. In a medical setting in which the testing techniques arerelied upon, for example before allowing a therapy to take place, theramifications associated with inaccurate testing can be serious. If thewater testing underreports the level of a certain substance in thetested water, the water can be allowed to be used when it should not be,resulting in a potentially unsafe condition for the patient or in themalfunctioning of a machine running a medical treatment for the patient.The reverse situation is also problematic. If the testing isoversensitive, or in any case gives false positive or over-reportedresults, the system may needlessly alarm or erroneously prevent atreatment from occurring.

Another problem with the above testing is its manual nature. Even if thetesting assay is otherwise sound, the patient or caregiver can introduceerror. And even if the testing and the operator performance are sound,manual testing still requires extra steps, adding time, complexity andcost.

An improved water quality system and method are needed accordingly.

SUMMARY

The present disclosure relates to water testing and in particular to thetesting of total chlorine in water. One application for the testingsystem and methodology of the present disclosure is to make water foruse with online hemodialysis. Online hemodialysis makes dialysate frompurified water. The purified water can be made from house tap water. Ina hospital or clinic, the house tap water is the water found for exampleat sinks and drinking fountains in the hospital or clinic. At home, thetap water is the patient's home tap water.

Making dialysate from purified tap water involves adding salts to thepurified water. The goal is to achieve the electrolyte status of bloodplasma, or the water component of blood. Because hemodialysis works onthe principles of osmosis, diffusion and/or equilibration, the treatmentneeds to use a treatment fluid, or dialysate, that has the chemicalcomposition of purified blood. There are many components to thepatient's blood that are healthy and needed and should not be removedduring treatment. Red and white blood cells and platelets are examples.But these healthy and needed components are retained mechanically bymaking the pores in the dialyzer membranes too small for the cells andthe platelets to pass through from the patient or blood side of thedialyzer to the treatment or dialysate side of the dialyzer.

Salts or electrolytes such as a potassium, calcium, sodium and magnesiumare also, at least to a certain extent, healthy and needed components ofblood. But salts are dissolved in the blood water or plasma. Thus ifpure water were to be run as treatment fluid instead of dialysate, thelarge osmotic or diffusive gradient would pull too much of the salt fromthe blood and create a highly unsafe condition for the patient. For thatreason, great care is taken in the online manufacture of dialysate frompurified water to ensure that a desired amount of salt is present in thedialysate before the dialysate is allowed to be delivered to thedialyzer and osmotically or diffusively comingle with the patient'sblood.

One method for ensuring that a desired amount of salt is present in thedialysate is through the use of conductivity sensors. Adding salt to thepurified water generator increases electrical conductivity sensed by thesensors. The desired amount of salt will have a specific conductivity.The online machine mixes pure water and salts from concentratecontainers until the desired conductivity is sensed, after which thedialysate can be delivered to the dialyzer.

The online hemodialysis system contemplated for use with the presentsystem and methodology employs a water purification system that removespreexisting salts (e.g., ions), such as chlorine, from the incoming tapwater so that the dialysate generation portion of the system can beginwith salt-less, zero-conductivity water to which desired, blood-friendlysalts are added. Also, free chlorine in dialysate can cross the dialysismembrane and destroy the patient's red blood cells. Free chlorine insolution can also generate chloramines, which are known to inducehemolytic anemia. The useful lifetime of dialysis membranes is alsoshortened when free chlorine is present in dialysate. For at least thesereasons, AAMI/ANSI recommends that dialysate contain less than 0.5 mg/Lof free chlorine.

The present system and method provides a way to automatically andprecisely detect either (i) the incoming total chlorine level of the tapwater or (ii) the total chlorine level present after the tap water hasflowed through a filter intended to remove impurities such as activechlorine compounds (e.g., a filter check). The system and method do notrequire input from the patient or caregiver. The system and method arealso accurate, so that the system alarms or otherwise responds whenchlorine levels are too high but greatly reduces the amount of falsetrips and needless treatment shutdowns.

In an embodiment, the system and corresponding method include a maintesting unit in fluid communication with an iodide reservoir and areducing agent reservoir. A membrane is provided with and divides themain unit into a reducing agent chamber and an iodide and water samplechamber, which are in fluid communication with the reducing agentreservoir and the iodide reservoir, respectively. The main unit furtherincludes two electrode pairs. A tri-iodide generation loop circuitincludes the two probes or electrodes of the first pair and bridges themembrane such that a first probe resides in the reducing agent chamberand a second probe resides in the iodide and water sample chamber. Asecond, tri-iodide detection circuit includes two probes, or electrodesboth of which are placed in the iodide and water sample chamber. In someembodiments, the iodide and water sample chamber is a tube disposedwithin the reducing agent chamber, which may also be a tube. In someembodiments, the iodide and water sample chamber is in fluidcommunication with the reducing agent chamber via microchannels, forexample in a cassette.

In an embodiment, water quality is tested by determining a level oftotal chlorine. In such an embodiment, a water sample is provided to theiodide and sample chamber of the main testing unit. Once the watersample is pumped to the iodide and sample chamber, a baseline voltage ismeasured and converted into a baseline current measurement. Then, avoltage is applied to the two electrodes of the tri-iodide generationloop circuitry. The voltage produces tri-iodide from the iodide source(e.g., KI and/or NaI). This production of tri-iodide causes current toflow through the electrodes of a detection circuit. The electrodes ofthe detection circuitry signal the amount of tri-iodide generated to acomputer or control unit by measuring voltage across a resistor producedwhen the current flows through the generation circuitry. The voltagemeasurement that takes place in the presence of total chlorine can alsobe replicated by applying current to the system to generate tri-iodideartificially. Because the amount of tri-iodide generated in thisartificial manner can be known by measuring the amount of currentapplied, it provides for an effective calibration of the measurementsystem, thereby enhancing accuracy.

In an embodiment, the concentration of total chlorine in water undertest is determined by first measuring an initial, background voltageassociated with any tri-iodide that may already be in the system (e.g.,without generating any tri-iodide or adding external tri-iodide). In oneembodiment, the background voltage or current (calculated using Ohm'slaw) is subtracted from subsequent voltage or current measurements. Thesample of water for testing is then added to the test chamber and abaseline voltage measurement is taken, which can then optionally beconverted into a baseline current reading using Ohm's law. This step isfollowed by repeated cycles of (a) generating tri-iodide by applicationof current to the generation circuit and (b) measuring the resultingvoltage in the detection circuit. The plurality of voltage measurements(or current measurements calculated from the plurality of voltagemeasurements) are plotted against relative or absolute tri-iodideconcentration. In this way, a calibration curve including a baseline,the test measurement, and several additional data points of knowntri-iodide concentration increases is created. The amount of totalchlorine present in the water under test is proportional to thedifference in tri-iodide concentrations from subsequent cycles asdescribed above.

In some embodiments, the concentration of total chlorine in the waterunder test is determined from (a) a background voltage or currentmeasurement, (b) a baseline voltage or current measurement, and (c) fromone to about twenty cycles of (i) generating tri-iodide by applicationof current to the generation circuit and (ii) measuring the resultingvoltage in the detection circuit. The choice of the number of cycles instep (c) will reflect a balance between accuracy of the total chlorinedetermination and the amount of time required to perform the analysis.More cycles generally lead to more accurate results. However, each cyclecan take from several seconds to several minutes depending on operatingparameters, and thus in the interest of providing efficient and safedialysis, the fewest number of cycles in step (c) required to provide anaccurate total chlorine determination is desired in one embodiment.Thus, in some embodiments, step (c) includes one to five cycles. In someembodiments, a first determination of total chlorine includes a largernumber of cycles in step (c), while subsequent determinations of totalchlorine include fewer cycles in step (c). For example and withoutlimitation, a first determination of total chlorine in water under testincludes three, four or five cycles in step (c). A subsequent or aplurality of subsequent total chlorine determinations then includes one,two or three cycles in step (c).

In some embodiments, the water sample is a purified water sample, forexample a sample of water that has been passed through a filtercomprising carbon. In some embodiments, the water sample is a sample ofdialysis water produced by a water purification machine.

In some embodiments, the testing system is in fluid communication with awater purification machine, which is in turn in fluid communication witha dialysis machine. In some embodiments, the dialysis machine isconfigured to stop or prevent a dialysis treatment if the testing systemdetermines that the total chlorine level of the sample of dialysis waterproduced by the water purification machine exceeds a predetermined level(e.g., about 0.1 ppm). In some embodiments, the testing system isconfigured to trigger an alarm or a notification on a display associatedwith the water purification machine and/or the dialysis machineindicating that the total chlorine level of the dialysis water exceeds apredetermined level (e.g., 0.1 ppm).

In some embodiments, the testing system includes a self-diagnosticfeature capable of identifying a fault in the testing system. In oneembodiment, the self-diagnostic feature compares a series of lag timesbetween tri-iodide generation and tri-iodide detection over time toidentify a fault in the testing system. In some embodiments, theself-diagnostic feature triggers an alarm indicating the fault statewhen the lag times exceed a predetermined level or increase beyond apredetermined level.

It is accordingly an advantage that the water purification system andmethod of the present disclosure is performed automatically.

It is another advantage that the water purification testing system andmethod of the present disclosure is calibrated automatically.

It is a further advantage that the water purification testing system andmethod of the present disclosure is cleaned automatically.

It is yet another advantage that the water purification testing systemand method of the present disclosure is accurate.

It is yet a further advantage that the water purification testing systemand method of the present disclosure is low cost.

It is still another advantage that the water purification testing systemand method of the present disclosure is built into or packaged with awater purification system.

It is yet a further advantage that the water purification testing systemand method of the present disclosure requires minimal maintenance.

Still another advantage is that the water purification testing systemand method of the present disclosure reduces user interaction.

Still a further advantage is that the water purification testing systemand method of the present disclosure outputs electrically for systemintegration.

Additional features and advantages are described herein, and will beapparent from, the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic view of one embodiment of a water purificationtesting system and method of the present disclosure.

FIG. 2 is a schematic view of one embodiment of a generation cell of thepresent disclosure.

FIG. 3 is a schematic view of one embodiment of a detection cell of thepresent disclosure.

FIG. 4 is a schematic view of one representation of a mechanism in whicha sodium sulfate anion promotes the conversion of three iodide anions toone tri-iodide anion and two electrons in water.

FIG. 5 is a graph showing chlorine concentration measured by a waterpurification testing system and method of the present disclosure versusactual chlorine concentration.

FIG. 6 is a graph showing an example calculation of a total chlorinelevel for a water sample according to the present disclosure.

FIG. 7 is a schematic view of one embodiment of a water treatment systemwhich includes a detection cell of the present disclosure.

FIG. 8 is a schematic view of one embodiment of a water treatment systemwhich includes a detection cell of the present disclosure.

FIG. 9 is a schematic view of one embodiment of a water treatment systemwhich includes a detection cell of the present disclosure.

FIG. 10 is a schematic view of one embodiment of a water treatmentsystem which includes a detection cell of the present disclosure.

DETAILED DESCRIPTION

As discussed above, a more accurate and easier to use total chlorinesensor is needed to minimize the occurrences of false positives or tripsinherent with other chlorine testing methods (e.g., testing strips).False positive results are problematic in the purification of water forhemodialysis because they force users to stop treatment and performmaintenance. False negatives may result in an unsafe treatment beingperformed. The testing system and method discussed herein greatlyreduces the false tripping, can detect at least as low as 0.05 parts permillion (“ppm”) total chlorine concentration in one implementation,provides an automatic detection function (including calibration),built-in packaging, and the ability to be implemented with a relativelysmall incremental cost. In other embodiments, the testing system andmethod is capable of detecting 0.01 ppm total chlorine.

As used herein, the term, “total chlorine” refers to any and allreactive chlorine compounds including, but not limited to, chlorine gas(e.g., dissolved chlorine gas), hypochlorite, chloramines, andchloramine-T. Total chlorine may but does not have to exclude chloridesalts (e.g., metal chlorides such as sodium chloride, potassiumchloride, etc.).

In one embodiment, the water purity testing apparatus and associatedmethodology are integrated into a water purification machine, such asone set forth in U.S. Patent Publication No. 2011/0197971, entitled,“Water Purification System And Method”, filed Apr. 25, 2011, which is inturn used with an online hemodialysis machine, such as one set forth inU.S. Patent Publication No. 2009/0101549, entitled, “Modular AssemblyFor A Hemodialysis System”, filed Aug. 27, 2008, the entire contents ofeach of which are incorporated herein by reference and relied upon. Theelectrical and/or computer control units discussed below may be locatedin the water purification machine and/or the dialysis machine. The pumpsand valves discussed below are located in one embodiment within thewater purification machine. Thus, there can be electrical cablingrunning from the dialysis machine to the water purification machine tocontrol the pumps and valves located within the water purificationmachine. Alternatively, the water purification machine can also houseits own electrical and/or computer control unit for controlling thepurification units, pumps and valves. Even here, however, the waterpurification control unit can communicate wired or wirelessly with thedialysis machine and be subordinate, for example, to the dialysismachine's master controller, e.g., sending chlorine data to same. Eitherone or both of the control units of the dialysis unit or the waterpurification unit could then place the overall system into an alarmstate if needed.

In one embodiment, the system and method of the present disclosuremeasure chlorine indirectly by allowing the molecule to oxidize iodideto tri-iodide and measuring the corresponding voltage change. Totalchlorine may be introduced into the system through many forms including,but not limited to, chlorine standard free chlorine (e.g., Cl₂ dissolvedin water), hypochlorite (e.g., as bleach), or chloramine-T. In apreferred embodiment, chloramine-T is used as a stabilized form of totalchlorine and is added to an iodide-containing reagent solution.Chloramine-T degrades to hypochlorite and hypochlorite in turn reactswith iodide via the following relationship to form tri-iodide:ClO⁻⁺³I⁻⁺²H⁺

I₃ ⁻+H₂O+CI⁻

Calibration of the electrode system is achieved by electrochemicallygenerating tri-iodide and measuring the system response (voltage).Tri-iodide may be generated in multiple sessions to improve theestimation of the dependence of voltage with changes in tri-iodideconcentration. The amount of tri-iodide generated is computed frommeasured current moving though the electrode placed into a potassiumiodide chamber. The current, in turn, is determined by measuring thevoltage change across a resistor of known value. Tri-iodide generationcan be accomplished using metals including, but not limited to, platinumand stainless steel, and by using SO₄ ⁻² as an auxiliary electrolyte. Inthis scenario, the electrochemical equations governing the generation oftri-iodide are:3I ⁻ →I ₃ ⁻⁺² e ⁻SO₄ ⁻²+2e ⁻⁺⁴H⁺→SO₂+2H₂O

In one preferred embodiment, sulfate ions are introduced through sodiumsulfate and iodide ions are introduced as potassium iodide. Sodiumsulfate concentrations and potassium iodide concentrations above 5 g/Lhave been seen to yield reproducible generations of tri-iodidemolecules. Also in a preferred embodiment, the generation voltage ismaintained by a voltage source set to deliver 700 mV. The correspondinggenerating voltage ranges from 0.5 to 3.5 V and depends on theconcentration of iodide and sulfate ions.

Referring now to the drawings and in particular to FIG. 1, in oneembodiment an, e.g. embedded, testing system 10 provides two reagentreservoirs including an iodide reservoir or cell 12 and a reducing agentreservoir or cell 14. Iodide reservoir or cell 12 includes an iodidesource. Any iodide source may be used, provided that the iodide sourcecompletely dissociates in water. Non-limiting examples of iodide sourcesinclude alkaline iodide reagents such as potassium iodide (KI) and/orsodium iodide (NaI). Reducing agent reservoir or cell 14 includes areducing agent. Any suitable reducing agent may be used, provided thatthe reducing agent readily accepts electrons. One non-limiting exampleof a reducing agent is an alkaline sulfate such as sodium sulfate(Na₂SO₄). In one embodiment, iodide reservoir or cell 12 includespotassium iodide and reducing agent reservoir or cell 14 includes sodiumsulfate. System 10 also includes a main testing unit 20 that operateswith two electrical control circuits 30 and 40. Main testing unit 20includes a liquid-tight housing 22, which is separated into twocompartments 24 and 26 by a semi-permeable membrane 28 to allow chargedions to pass through the membrane, preventing an open circuit. Housing22 can be metal or plastic as desired. Compartments 24 and 26 can beopened or closed and be sized to be the same or to have differentvolumes as desired. Membrane 28 can be a semipermeable membrane made ofa suitable material including polyether sulfone, cellulose, nylon,and/or any other semipermeable membrane with a molecular weight cutoff(“MWCO”) of about 1,000 Daltons, in one preferred embodiment about 500Daltons, and in another preferred embodiment from about 100 Daltons toabout 500 Daltons. In some embodiments, membrane 28 is Ultracel PL-1from Millipore (MWCO 1000). In some embodiments, the membrane allowsonly positive charge to penetrate. In some embodiments, the membraneallows only negative charges to penetrate. In some embodiments, themembrane allows both positive and negative charges to penetrate.

Reagent reservoirs 12 and 14 are both in valved and pump communicationwith main testing unit 20. In an embodiment, the iodide reservoir 12and/or the reducing agent reservoir 14 are provided in a cartridge orcassette form. In an embodiment, the cartridge or cassette includesiodide reservoir 12 and reducing agent reservoir 14. In anotherembodiment, the cartridge includes iodide reservoir 12, reducing agentreservoir 14, and electrodes 42 a and 42 b for tri-iodide generationcircuitry 40 and/or electrodes 32 a and 32 b for tri-iodide detectioncircuitry 30. In an embodiment, the iodide is provided in a liquid formsuch as a pre-mixed solution or a concentrate, or in a solid form suchas a crystal, a powder, and/or a tablet. In an embodiment, the reducingagent is provided in a liquid form such as a pre-mixed solution or aconcentrate, or in a solid form such as a crystal, a powder, and/or atablet. When either chemical is provided in dry form, the associatedcontrol unit can control the associated pumps and valves to first pumpwater into the crystal, dry powder or tablet containers for mixingbefore pumping liquid iodide or reducing agent from the containers.

In the embodiment illustrated in FIG. 1, the iodide cell or reservoir 12communicates fluidly with the iodide and sample chamber or compartment24 of main testing unit 20 via line 52 a including a valve 16 a and pump18 a. Reducing agent cell or reservoir 14 in turn communicates fluidlywith chamber or compartment 26 of main testing unit 20 via line 52 bincluding valve 16 b and pump 18 b.

FIG. 1 also illustrates that the main testing unit 20 is fluidlyconnected to a water purification unit or machine 50, which can be thewater purification machine described above in the incorporated U.S.2011/0197971 Publication. In the illustrated embodiment, there aremultiple connections between water purification machine 50 and maintesting unit 20. In particular, test water is pumped from a test wateroutlet or supply 58 of water purification machine 50 to KI and samplechamber or compartment 24 of main testing unit 20 via line 52 c,including valve 16 c and pump 18 c. Deionized (“DI”) water is pumpedfrom DI water outlet or supply 56 of water purification machine 50 toiodide and sample compartment 24 of main testing unit via line 52 d,including valve 16 d and pump 18 d. Drainage water is pumped from theiodide and sample compartment 24 of main testing unit 20 to a drain 54of water purification machine 50 via line 52 e, including valve 16 e andpump 18 e.

Drainage water is also pumped from reducing agent chamber or compartment26 of main testing unit 20 to drain 54 of water purification machine 50via line 52 f, including valve 16 f and pump 18 f. DI water is alsopumped from DI water outlet or supply 56 of water purification machineto reducing agent compartment 26 of the main testing unit via line 52 g,including valve 16 g and pump 18 g.

In an alternative embodiment, a single drain pump (18 e or 18 f) is usedinstead of the separate drain pumps illustrated and drain valves 16 eand 16 f are sequenced to selectively drain from one or both of chambersor compartments 24 and 26. Alternatively or additionally, a single DIpump (18 d or 18 g) is used instead of the multiple DI pumps illustratedand DI valves 16 d and 16 g are sequenced to selectively pump DI waterto one or both of chambers or compartments 24 and 26. Thus, the numberof pumps shown in FIG. 1 can be reduced by at least two pumps from thenumber of pumps illustrated.

As described in further detail below, chlorine testing is performedusing the valves and pumps provided or operable with lines 52 a to 52 cin association with the control circuit 30 and electrode pair 32 a and32 b. Calibration is performed using the valves and pumps provided oroperable with lines 52 a, 52 b, 52 d and 52 g in association withcontrol circuits 30 and 40 and their respective electrode pairs 32 a/32b and 42 a/42 b. Rinse is performed using the valves and pumps providedor operable with lines 52 d to 52 g.

In an embodiment, pumps 18 a to 18 g are electrically operated pumps,such as microfluidic pumps, and can be gear, centrifugal, piston or vanepumps. The pumps may have liquid contacting surfaces that are made ofmedical grade plastic or stainless steel, such that the surfaces cannotthemselves corrode or contaminate water, such as test, DI or drainwater, running past the surfaces, or they may have liquid contactingsurfaces that may contaminate the fluid if placed in the drain line. Inan alternative embodiment, pumps 18 a to 18 g are small peristaltic(roller or linear) or tube actuating (e.g., shuttle) pumps that pumpwater, such as test, DI or drain water, through a respective tube bycollapsing, squeezing and/or crushing the tube sequentially to move thefluid. In another alternative embodiment, pumps 18 a to 18 g areelectrically and/or pneumatically actuated membrane pumps that movewater, such as test, DI or drain water, by fluctuating a membrane backand forth between a chamber of known volume. Pumps 18 a to 18 g canfurther alternatively be any combination of the above types of liquidpumps, selected to optimize performance, cost and reliability.

It should be appreciated from the above discussion of the various typesof pumps 18 a to 18 g, that lines 52 a to 52 g can be made of differentmaterials, such as stainless steel or plastic. Suitable plastics includepolyvinylchloride (“PVC”), for example, when lines 52 a to 52 g do nothave to be deformed for, e.g., peristaltic or shuttle, pumping, orsilicone, for example, when lines 52 a to 52 g are deformed for, e.g.,peristaltic or shuttle, pumping. If membrane pumps are used, lines 52 ato 52 g may contain sections that transition to a chamber havingmembrane sheeting, which can likewise be plastic, such as PVC sheeting.

Each of valves 16 a to 16 g can be an electrically or pneumaticallyactuated valve. In an embodiment, valves 16 a to 16 g include a valvehousing to which the respective line 52 a to 52 g is sealingly attached.Here, each line 52 a to 52 g can be broken and sealingly attached toinlet and outlet connectors of the respective valve 16 a to 16 g. Also,here the valve includes its own internal opening/shutting mechanism.Alternatively, valves 16 a to 16 g are electrically or pneumaticallyactuated solenoid valves that operate directly on lines or tubes 52 a to52 g, e.g., compressible plastic tubes. The solenoid valves can forexample be fail-safe or spring-operated closed and electrically orpneumatically actuated open. In a further alternative embodiment, valves16 a to 16 g are electrically and/or pneumatically actuated membranevalves, for example, provided as part of a disposable cassette thatincludes a hard, valve chamber part that is sealed fluidly by one ormore flexible, e.g., PVC, sheet that is flexed to close and open thehard part of the chambers. Here, the hard part can also be formed withpump chambers and the same one or more flexible sheet can be used forpumps 18 a to 18 g. Valves 16 a to 16 g can further alternatively be anycombination of the above types of liquid valves, selected to optimizeperformance, cost and reliability.

System 10 includes a control unit 60, which in the illustratedembodiment is housed inside water purification machine 50. Control unit60 can include one or more processor, one or more memory and one or morecontrol circuitry, such as control circuits 30 and 40. Pumps 18 a to 18g and valves 16 a to 16 g can be operated under the control of acomputer program stored at control unit 60. Control unit 60 is in oneembodiment the same control unit 60 used for all of water purificationmachine 50. Hence, control unit 60 may include a master processor thatcommunicates (i) with a user interface 62 of water purification machine50, (ii) with a wired or wireless data link to a corresponding controlunit 110 of dialysis machine 100 that uses water produced by waterpurification machine 50, and (iii) with one or more delegate processorthat runs the electrical equipment provided within water purificationmachine 50, including pumps 18 a to 18 g and valves 16 a to 16 g. Eitherone or both of the master and delegate processors of control unit 60 mayreceive signal inputs from and send signal outputs to control circuits30 and 40.

In one embodiment, the master processor sends output data, such aschlorine content output data, to one or both of a user interface ofwater purification machine 50 and/or to the control unit 110 of thedialysis machine 100. It is contemplated for dialysis machine 100 to siton top of water purification machine 50. Thus, either user interface 62of water purification machine 50 and/or user interface 112 of dialysismachine 110 could be used to inform the patient or caregiver of thechlorine results and to communicate any associated alerts or alarms. Inone embodiment, however, main user interface 112 of dialysis machine 110is a wireless, e.g., tablet, user interface that allows the patient orcaregiver to reside remotely from the dialysis machine while stillviewing information concerning same. Here, it is desirable to send waterpurification machine 50 data, such as chlorine content data, via controlunit 60 to control unit 110 of dialysis machine 100, which in turnforwards the pertinent data to remote user interface or tablet 112.

In an alternative embodiment, the generation and receipt of signals toand from control circuits 30 and 40 and the control of pumps 18 a to 18g, valves 16 a to 16 g and possibly other electrical components of waterpurification machine 50 is done via control unit 110 of the dialysismachine 100. Here again, control unit 110 of dialysis machine 100 canforward pertinent data to the remote user interface or tablet 112 of thedialysis machine 100. When control unit 110 of machine 100 is theprimary control unit for water purification system 10, control unit 60may be eliminated, at least as far as system 10 is concerned, or limitedto a smaller number of tasks.

In any case, control unit 60 and/or control unit 110 opens valves 16 ato 16 g and operates pumps 18 a to 18 g to meter into compartments 24and 26 precise amounts of desired fluids, e.g., DI water, iodidesolution, reducing agent solution or test water solution, or to removeprecise amounts of fluids from chambers or compartments 24 and 26 todrain 54. The metering can be run open loop and rely on the accuracy ofthe pumping mechanism to deliver the correct ratio of fluids.Alternatively or additionally, feedback in the form of conductivitysensing may be used to ensure that the proper proportioning of fluidstakes place within chambers or compartments 24 and 26.

As illustrated, in an embodiment, main unit 20 is placed in fluidcommunication with deionized water via outlet or storage 56 from waterpurification unit 50. Deionized water is pumped into the main unit(e.g., into the chambers or the compartments 24 and 26 separately) toflush the water test sample and any residual tri-iodide and/or totalchlorine from the main unit. In some embodiments, the total chlorinelevel is determined before and/or during each dialysis treatment. Here,an aliquot of water from water purification unit 50 for making dialysateis diverted to system 10 and analyzed by the methods disclosed hereinbefore any water from purification unit 50 is allowed to be used to makedialysate at machine 100. Control unit 60 or 110 can be programmed toprevent and/or suspend dialysis fluid preparation when the totalchlorine level in the dialysis water exceeds a threshold level, forexample 0.1 ppm. In some embodiments, water from purification unit 50 isanalyzed after a dialysis treatment is completed, such that correctiveaction can be taken to reduce total chlorine levels in the water beforea subsequent dialysis treatment is required, and providing typically atleast twenty-four hours before the subsequent treatment.

As discussed above, system 10 can be implemented within waterpurification unit 50. If so, main unit 20 can be positioned downstreamof one or more filter used in water purification unit as specified inthe U.S. 2011/0157971 Publication. For example and without limitation,main unit 20 may be in fluid communication with a carbon filter, whereinwater exiting the carbon filter, or samples thereof, is then tested fortotal chlorine compounds according to the present disclosure. A failedtest likely means that the carbon filter is faulty or spent and needsreplacement. A suitable message can then be displayed, e.g., on userinterface 112 of dialysis machine 100.

Electrical circuit 40 operates via a pair of electrodes 42 a and 42 b toperform calibration. Electrode 42 a is inserted into iodide and samplecompartment 24, while electrode 42 b is inserted into reducing agentchamber or compartment 26. Electrodes 42 a and 42 b can be metallic. Insome embodiments, electrodes 42 a and 42 b are each provided with or arein electrical communication with a resistor (e.g., a 1 kΩ resistor). Asdescribed above, the iodide solution and the reducing agent solution areseparated by membrane 28, which permits electricity but not fluid toflow across the membrane. In one embodiment, membrane 28 includesmicropores or perforations in the membrane, which are formed such thatthere are about three (3) to about twenty (20) holes, each hole sizedsuch that charge can freely pass between the chambers without any fluidpassing between the chambers. In one example embodiment, the membrane isformed of a silicone elastomeric material and includes about sevenmicropores formed by a 28-gauge needle. The elastomeric nature of themembrane causes the holes to substantially close, allowing electricalcharge to pass through without permitting fluid to pass between thechambers. One suitable membrane 28 is made of silicone tubing. Anothersuitable membrane 28 is provided by Millipore and is sold under thetrade name ULTRACEL PL-1. When a voltage is applied to electricalcircuit 40 (e.g., about 1 volt DC), the induced current generatestri-iodide from the iodide solution.

As discussed above, system 10 includes electrical control circuits 30and 40. Electrical circuit 30 operates via a pair of electrodes 32 a and32 b, which are each inserted into iodide and sample chamber orcompartment 24 of main testing unit 20.

Electrical circuit 30 detects the amount of tri-iodide generated at orby electrical control circuit 40. In some embodiments, electricalcircuit 30 is a tri-iodide detection circuit in which each electrode 32a and 32 b is carbon-based or metallic (e.g., metallic, platinum,stainless steel, gold, combinations and alloys thereof). At least one ofthe electrodes 32 a or 32 b can include or be in electricalcommunication with a resistor (e.g., a 5 kΩ resistor). In theillustrated embodiment, both electrodes 32 a and 32 b are in contactwith the fluid held within iodide and sample compartment 24. When a lowvoltage is applied across electrodes 32 a and 32 b, the current inducedcan be measured and used as a proxy for the amount of tri-iodide in thesolution, and therefore the amount of total chlorine in the watersample. In some embodiments, the system 10 formulated as just describedis capable of determining an amount of total chlorine in the watersample as low as about 0.1 ppm.

In one embodiment shown in the sectioned view of FIG. 2, testing unit 20is provided, at least in part, as a tubing assembly 200. The iodide andsample chamber or compartment 24 is a tube 214 disposed within areducing agent chamber or compartment 26, which is also a tube 216, andwhich is of a larger diameter than that of tube 214 (chamber 24). Insome embodiments, the outer reducing agent tube 216 has an innerdiameter that is about 1.5 to about 4 times larger the outer diameter ofthe inner iodide and sample tube 214. Tube 214 (chamber 24) is in fluidcommunication with iodide reservoir 12 (not illustrated in FIG. 2),while tube 216 (chamber 26) is in fluid communication with reducingagent reservoir 14 (not illustrated in FIG. 2). The inner iodide andsample tube 214 includes or defines a plurality of perforations 214 a(membrane 28), e.g., hydrophobic perforations, which do not allow fluidto pass between chambers 24 and 26, but permit electrical conductivityto flow between the chambers (through the wall of narrower tube 214 intothe outer diameter of larger tube 216).

The inner iodide and sample tube 214 is also in fluid communication withwater to be tested (not illustrated in FIG. 2), which is pumped via line52 c and pump 18 c from test sample outlet 58 of water purificationmachine 50. The tri-iodide generation loop of electrical circuit 40includes electrodes 42 a and 42 b, each having or being in electricalcommunication with a respective resistor 46 and 48 (e.g., a 1 kΩresistor). Electrode 42 a of electrical circuit 40 is placed in contactwith the fluid in the inner iodide and sample tube 214, while the otherelectrode 42 b is placed in contact with the fluid in the outer reducingagent tube 216. In the illustrated embodiment, electrode 42 b isgrounded. As mentioned above, electrodes 42 a and 42 b can be formed ofdurable metal such as platinum, stainless steel, gold, copper, or becombinations or alloys thereof.

A voltage source 44 is provided (e.g., as part of electronics 40 or aspart of control unit 60 or 110) to apply of a voltage, such as fromabout 0.7 VDC to about 1.0 VDC. The voltage source across the setresistance of resistors 46 and 48 generates a desired current. Theapplied current generates tri-iodide in the iodide and sample tube 214(chamber 24).

The tri-iodide generated by tri-iodide generation circuit 40 travelsalong pathway P (shown in FIG. 2) towards tri-iodide detection cell 30,one embodiment of which is shown in FIG. 3. Tri-iodide detection cell 30includes two electrodes 32 a and 32 b. In some embodiments, electrodes32 a and 32 b are formed of carbon or a durable metal, such as platinum,stainless steel, gold, copper, or combinations or alloys thereof, andare in contact with the fluid in the iodide and sample compartment 24provided here by inner tube 214. Electrode 32 b includes or is inelectrical communication with a resistor 36, which may be for example a5 kΩ resistor. In some embodiments, electrodes 32 a and 32 b areshielded or coated in a manner such that the proportion of theelectrodes exposed to fluid remains constant throughout the testingprocess even if iodide and sample compartment 24 is moved somehowrelative to the electrodes. Application of a low voltage (e.g., about100 mVDC) from a voltage source 34 (e.g., of electronics 30 or ofcontrol units 60 or 110) induces a current across electrodes 32 a and 32b and the set resistance of resistor 36. The voltage across the resistor36 is measured and stored and/or recorded, e.g., at control unit 60 or110, and is used to calculate the current across electrodes 32 a and 32b. The voltage (or calculated current) is proportional to the amount oftri-iodide generated by the tri-iodide generation circuit 40. In oneembodiment, the voltage measured in the tri-iodide detection cell 30 isa steady state voltage. Sensor 38 can be configured to output to controlunit 60 or 100.

In one embodiment, iodide reservoir 12 is a chamber holding an alkalineiodide solution of known concentration (for example a solution having aknown amount of an alkaline iodide such as KI and/or NaI in a knownamount of water), and which is in fluid communication with the iodideand sample chamber 24 as shown and discussed above. In some embodiments,iodide reservoir 12 holds about 0.1 gram to about one gram of iodidesalt(s) (e.g., an alkaline iodide such as KI and/or NaI) in about one toabout ten mL of water. In some embodiments, the iodide solution is asolution of 0.25 gram to 0.7 grams of iodide salt(s) (e.g., an alkalineiodide such as KI and/or NaI) in three to seven mL of water. In someembodiments, iodide reservoir 12 contains at least enough iodide salt(s)to last about one month or longer, e.g., from one month to six months,for example, so that refilling iodide reservoir 12 does not reduce thenormal maintenance cycle of water purification unit 50. In someembodiments, the iodide solution itself has a level of total chlorinethat is below the detection limit for the system. In some embodiments,the iodide solution has less than 0.1 ppm, less than 0.05 ppm, or lessthan 0.01 ppm of any total chlorine compound.

Reducing agent reservoir 14 is a chamber holding a solution including aknown amount of one or more reducing agents (e.g., an alkaline sulfatesuch as Na₂SO₄). In some embodiments, the reducing agent reservoirincludes about two to about twenty grams of reducing agent (e.g., analkaline sulfate such as Na₂SO₄) in a suitable amount of water. In someembodiments, the reducing agent reservoir 14 holds about seventeen gramsof Na₂SO₄. In some embodiments, reducing agent reservoir 14 contains atleast enough reducing agent (e.g., an alkaline sulfate such as Na₂SO₄)to last about one month or longer, e.g., from one month to six months,for example, so that again refilling reducing agent reservoir 14 doesnot reduce the normal maintenance cycle of water purification unit 50.

In an embodiment, tri-iodide is generated in a water test sample by thetri-iodide generation circuitry 40 according to the parameters shown inthe following Table 1. In such an embodiment, resistors 36, 46 and 48are each 1 kΩ, and the liquid impermeable silicone elastomeric membrane(e.g., at 28 or 214 a) includes nine holes each formed by piercing themembrane with a 28-gauge needle, the holes then substantially closingdue to the compressive elasticity of the membrane as described above.The concentration of iodide in the iodide reservoir 12 in the example is66,667 ppm, with potassium iodide (KI) or another iodide sourcedissolved in water such that the total iodide solution volume is 4 mL incompartment 24. The concentration of the reducing agent in the reducingagent reservoir 14 is about 75,000 ppm, with sodium sulfate or anotherreducing agent dissolved in water. A voltage of about 0.7 VDC is appliedacross circuit 40 for about one minute.

TABLE 1 Generation Cell Specifications Parameter Value Voltage 0.7 VGeneration Time 1 minute Resistor 1 kΩ (0.983 kΩ) Perforations 9 holesproduced by a 28-gauge needle Potassium iodide volume 4 mL (shared withdetection cell) Potassium iodide concentration 66,667 ppm Sodium sulfateconcentration 75,000 ppm

In one example, the tri-iodide concentration is determined using atri-iodide detector cell 30 having the parameters shown in Table 2. Avoltage of about 0.1 VDC is applied for about five minutes across thetri-iodide detector cell having a 5 kΩ resistor. The induced current ismeasured by conventional current, or via voltage meter with knownresistance, and compared against a standard curve to determine the totalchlorine content of the water test sample. The standard curve isdiscussed in more detail below.

In an embodiment, the detector cell 30 continuously determines thevoltage across the resistor 36. In such an embodiment, the detector cell30 can also be used to diagnose one or more performance issue in thesystem 10. For example, due to mass transfer and based at least in parton the size of the chambers 24 and 26 and the identity andcharacteristics of membrane 28, a change (e.g., an increase) in a lagtime between the application of a voltage to electrode pair 32 a and 32b and the detection of an increase in voltage or current in the detectorcell 30 may indicate failure of a pump (e.g., one or more of pumps 18 ato 18 f), a valve (e.g., one or more of valves 16 a to 16 f), themembrane 28, electrode pair 32 a and 32 b, electrode pair 42 a and 42 b,or a combination of the foregoing.

In an embodiment, control unit 60 or 110 automatically performs multipletotal chlorine determinations and averages the discrete results. It iscontemplated for system 10 to use an agitator, such as an ultrasonicvibrator to agitate testing unit 20 during the test cycle to promoteconnectivity between the tri-iodide generation loop 40 and thetri-iodide detection cell 30.

TABLE 2 Detection Cell Specifications Parameter Value Voltage 0.1 VEquilibration Time 4 minute Resistor 5 kΩ (4.91 kΩ) Potassium iodidevolume 4 mL (shared with generation cell) Potassium iodide concentration66,667 ppm

Example Methodology

Using system 10, control unit 60 or 110 can operate according to onemethodology as follows:

-   -   (a) providing a total chlorine detection system as disclosed        herein;    -   (b) providing a water sample, the water sample including an        amount of total chlorine;    -   (c) measuring a background current in a tri-iodide detection        circuitry or cell 30, the background current associated with        tri-iodide present in the system before introduction of the        water sample;    -   (d) metering an amount of the water sample into the system;    -   (e) generating a first amount of tri-iodide by the reaction of        the total chlorine with iodine in the system;    -   (f) monitoring a baseline current in a tri-iodide detection        circuitry or cell 30, the baseline current associated with the        amount of tri-iodide in the water sample;    -   (g) generating a second, known amount of tri-iodide from the        water sample by a tri-iodide generation circuitry or loop 40;    -   (h) monitoring a second current induced in a tri-iodide        detection circuitry or cell 30, the second current associated        with the sum of the first and second amounts of tri-iodide;    -   (i) generating a third, known amount of tri-iodide from the        water sample by the tri-iodide generation circuitry or loop 40;    -   (j) monitoring a third current induced in the tri-iodide        detection circuitry or cell 30, the third current associated        with the sum of the first, second and third amounts of        tri-iodide;    -   (k) optionally generating a fourth, known amount of tri-iodide        from the water sample by the tri-iodide generation circuitry or        loop 40;    -   (l) optionally monitoring a fourth current induced in the        tri-iodide detection circuitry or cell 30, the fourth current        associated with the sum of the first, second, third and optional        fourth amounts of tri-iodide; and    -   (m) calculating the total chlorine concentration in the water        sample using the baseline current, the second monitored current,        the third monitored current, and the optional fourth monitored        current, wherein each of the currents is optionally corrected by        first subtracting the background current.

The calculation step (m) can be accomplished using any suitable dataanalysis means based on one or more of the baseline current and firstmonitored current, second monitored current, optional third monitoredcurrent, and optional fourth monitored current. In an examplemethodology, calculating the total chlorine concentration in the watersample in step (m) above includes:

-   -   (i) plotting the first, second, third and optional fourth        current values (y-axis), optionally corrected by subtracting the        background current, as a function of relative tri-iodide        concentration, wherein the first relative tri-iodide        concentration as determined in step (f) is set to x=0; and    -   (ii) extrapolating a line of best fit using at least two of the        second, third and optional fourth current values (each        optionally corrected by subtracting the background current) to a        point where y is equal to the baseline current and correlating        said point to determine the x-value (“x₀”), associated with said        point, wherein the unknown total chlorine concentration is equal        to (−1)(x₀).

In some embodiments, control unit 60 or 110 can cause an amount of timebetween a monitoring step and a subsequent tri-iodide generating step(e.g., between steps (f) and (g), between steps (h) and (i), and/orbetween steps (j) and (k)) to be no less than one minute, for examplefrom about one minute, anywhere to about ten minutes. In someembodiments, control unit 60 or 110 causes an amount of time between atri-iodide generating step and the correlating current monitoring step(e.g., between steps (e) and (f), between steps (g) and (h), betweensteps (i) and (j), and/or between steps (k) and (l)) to be no less thanabout one minute, for example from about one minute, anywhere to aboutten minutes. In some embodiments, control unit 60 or 110 causes currentto be monitored in one or more of steps (f), (h), (j), and/or (l) for noless than one minute, for example from about one minute, anywhere toabout ten minutes.

In any embodiment described herein, the monitored currents can becorrected to exclude any background tri-iodide present in the system bysubtracting the background current from each monitored current value. Inother embodiments, background tri-iodide present in, for example, theiodide reagent, can be reduced, minimized or eliminated by reversing thepolarity of the tri-iodide generation electrode and applying a suitablevoltage for a period of time sufficient to convert any backgroundtri-iodide to iodide before introduction of a water sample.

In some embodiments, a mechanism is included to adequately mix waterunder test with the iodide reagent. For example, the testing system mayinclude an agitator, a vibration mechanism, one or more baffles, astirrer, or any other suitable stirring mechanism. The mixer can beinvasive, such as a rotating mixer, or be non-invasive, such as avibrator that vibrates the outside of the reservoir.

In one ideal implementation, control unit 60 or 110 causes one unit(e.g., mole) of tri-iodide to be generated for each unit (e.g., mole) oftotal chlorine. In some embodiments, control unit 60 or 110 causes thepump speeds of one or more or all of concentrate pumps 18 a and 18 b andtest sample pump 18 c to be adjusted to optimize the ratio of the molesof tri-iodide formed per moles of total chlorine in the water undertest. In some embodiments, a higher pump speed generates closer to aboutone mole of tri-iodide per mole of total chlorine than a slower pumpspeed under otherwise identical conditions.

In some embodiments, chloramine-T is used as an artificial totalchlorine source to optimize or calibrate pump speed based on themeasured current in the tri-iodide detection cell. In such embodiments,a water sample with known total chlorine concentration may be preparedby combining a water sample with no or essentially no total chlorinecontent with a known amount of chloramine-T. The resulting water samplehaving a known total chlorine concentration may then be used to test thesensor, calibrate the system, or optimize pump speed.

In some embodiments, the testing system can be manually calibrated usinga series of water samples each having a known amount of total chlorine(e.g., a series of chloramine-T solutions of known concentration). Insuch embodiments, the testing system can be manually calibrated, and thetesting method may include (a) determining a background voltage orcurrent measurement, and (b) determining an amount of total chlorine inwater under test by (i) monitoring a baseline current in the detectioncircuit, (ii) generating tri-iodide by application of current to thegeneration circuit, (iii) measuring the resulting voltage in thedetection circuit, and (iv) comparing the voltage measured in thedetection circuit to the manually-derived calibration curve to calculatethe amount of total chlorine in the water under test.

Determination of the total chlorine content of the water test sample issensitive to the volume of the water test sample provided. Accordingly,in an embodiment, the amount of test sample water is accurately meteredand/or pumped into main test unit 20 by, for example, a microfluidicpump as discussed above. One suitable microfluidic pump is theSmoothFlow™ by Microfluidica, LLC (Glendale, Wis.). Although any amountof water under test may be used, typically a small volume, for examplefrom about 50 μL anywhere to about 500 μL of water under test is pumpedinto main testing unit 20.

FIG. 4 illustrates the principle of the electrochemical reaction. Inaqueous solution, one equivalent of sulfate (SO₄ ⁻²) promotes theconversion of three iodide anions (I⁻) to one tri-iodide anion (I₃ ⁻).The process consumes four equivalents of protons while producing oneequivalent of SO₂ and one equivalent of water, and simultaneouslyliberating two electrons (e⁻). When iodide anions are present in excesscompared to the amount of total chlorine, the amount of tri-iodideproduced is directly proportional to the amount of total chlorinepresent.

FIG. 5 demonstrates the accuracy of one embodiment of the presentlydisclosed system and method using chloramine-T as an artificial sourceof total chlorine in water under test. The chlorine content of threetest solutions of known chlorine concentration (0.05 ppm, 0.1 ppm and0.2 ppm) were determined using the parameters of Tables 1 and 2 above.As shown in FIG. 5, system 10 and the corresponding method are accurateeven for ultra-low chlorine concentrations (e.g., 2 ppm total chlorineor less). The dashed line shows the ideal measurement (slope=1). Thesystem is accurate within 3% at 0.1 and 0.2 ppm, and within 8% at 0.05ppm. Error bars indicate 95% confidence levels at each data point.

In an embodiment, the total chlorine content of the water under test canbe calculated by any analytical means from the baseline current and theone or more tri-iodide-related current values. For example, theconcentration of tri-iodide generated ([I₃ ⁻]) can be determined fromthe current (i) according to the following relationship:[I ₃ ⁻ ]=i*t/2F*V,where i=current (A or charge/s), t=time (s), F=Faraday's constant(charge/mole of electrons), V=iodide reagent solution volume in liters,and 2 represents the number of electrons transferred between iodide andtri-iodide.

FIG. 6 shows an example chlorine determination according to the processdescribed above. The baseline current corresponds to baseline point 601.Point 602 corresponds to the first current and first tri-iodideconcentration. Point 603 corresponds to the second current and secondtri-iodide concentration. Point 604 corresponds to the third current andthird tri-iodide concentration. A standardized curve or line of best fit605 is determined using points 602, 603 and 604. The concentration ofchlorine (x₀) in the water under test is determined by determining thex-intercept of line of best fit 605 for baseline current 601.

Example Operation

Using system 10, one example operation stored at control unit 60 or 110is as follows:

-   -   Step 1. Add 0.25 gram to 0.7 gram of KI and three mL to seven mL        of water to the KI reservoir, and two grams to twenty grams of        Na₂SO₄ and 225 mL water to the Na₂SO₄ reservoir.    -   Step 2. 200 μL of water under test are then pumped via a        microfluidic pump into the KI/water sample chamber of the main        unit.    -   Step 3. 700 mV is then applied to electrode pair 42 a and 42 b        to generate tri-iodide. Optionally, the main unit is agitated to        promote mass transfer between the electrode pairs 32 a/32 b and        42 a/42 b.    -   Step 4. 100 mV is then applied to electrode pair 32 a and 32 b,        and the current is calculated from the voltage measured across        resistor 36 and is recorded.    -   Step 5. Steps 2 to 4 are repeated twice.    -   Step 6. Lines 52 d, 52 e and 52 f are then opened and the main        unit is flushed with DI water.    -   Step 7. The current recorded in Step 4 is used in comparison to        calibration data derived from testing the system with known        amounts of total chlorine (see, e.g., Example 2, below) to        calculate a level of total chlorine in the water under test.        This result can be displayed on a display device (e.g., display        device tablet 112 of a dialysis machine 100 or display device 62        of water purification machine 50), and/or an indicator (such as        an audible alarm and/or a visual alarm) can be used to notify a        user when the amount of total chlorine in the water under test        is above (or below) a predetermined threshold (e.g., 0.1 ppm).

Water Purification and Dialysis Machine Configuration Using the ChlorineSensing System

As discussed herein, water purification machine 50 can house or operatewith the chlorine sensing system 10 of the present disclosure. To thatend, chlorine sensing system 10 may be in fluid connection with waterpurification machine 50 at any suitable location along the fluid path ofthe machine. Referring now generally to FIGS. 7 to 10, in oneembodiment, a water purification machine 50 is in fluid connection witha water source 310. Water source 310 may be any water source suitablefor home use including, for example, a municipal water source or a wellwater source. In the illustrated embodiment, water purification machine50 includes a water pretreatment filter 320, which may include anynumber of filters and/or sorbents for removing impurities from the waterobtained from the water source 310. In some embodiments, the waterpretreatment filter 320 includes a carbon filter. In the embodimentshown in FIG. 7, water pretreatment filter 320 is in fluid connectionwith chlorine sensing system 10 as described herein. In this embodiment,chlorine sensing system 10 is also in fluid connection with a reverseosmosis filter 330. Reverse osmosis filter 330 is in turn in fluidconnection with a drain 370 and an electrodeionization (“EDI”) module340, which in turn may optionally further include an electrodialysiscomponent. The EDI module 340 is in fluid connection with an ultravioletlamp or filter 350, which in turn is in fluid connection with abacterial filter 360. Bacterial filter 360 may optionally furtherinclude an endotoxin filter. Water treated by water purification machine50 may be used with a downstream dialysis machine 100, such as ahemodialysis system or home hemodialysis machine as has been describedherein.

As illustrated in FIGS. 8 to 10, chlorine sensing system 10 mayalternatively be in fluid connection with the ultraviolet lamp or filter350 and the bacterial filter 360 (FIG. 8); with the bacterial filter 360and dialysis machine 100 (FIG. 9); or with the water source 310 and thewater pretreatment filter 320 (FIG. 10). In some embodiments, thechlorine sensing system 10 is in fluid connection with the water pathwayof the water purification machine 50 via a sampling port (not shown).

Aspects of the Present Disclosure

Aspects of the subject matter described herein may be useful alone or incombination with one or more other aspect described herein. Withoutlimiting the foregoing description, in a first aspect of the presentdisclosure, a dialysis system includes (i) a water purification machineproducing an at least partially purified water sample, (ii) a dialysismachine for providing dialysis therapy to a patient, the dialysismachine receiving purified water from the water purification machine,and (iii) a chlorine detection component for determining a level oftotal chlorine in the at least partially purified water sample, whereinthe chlorine detection component includes (a) an iodide reservoir, (b) areducing agent reservoir, (c) a first chamber in fluid communicationwith the iodide reservoir and the water purification machine, (d) asecond chamber in fluid communication with the reducing agent reservoir,wherein the first and second chambers are separated by a membrane thatallows charge but not fluid to pass between the chambers, (e) a firstelectrode pair associated with a first voltage source, wherein oneelectrode of the first electrode pair is in contact with iodide fluidand the at least partially purified water sample mixed in the firstchamber and the other electrode of the first electrode pair is incontact with a reducing agent solution in the second chamber, and (f) asecond electrode pair associated with a second voltage source, whereinboth electrodes of the second electrode pair are in contact with theiodide fluid and the at least partially purified water sample mixed inthe first chamber.

In accordance with a second aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,at least one of the electrodes includes carbon and/or a conductive metalsuch as platinum, gold, stainless steel, copper, combinations or alloysthereof.

In accordance with a third aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,at least one of the first and second chambers includes a tube.

In accordance with a fourth aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,the first and second chambers both include tubes, and wherein the firstchamber is disposed within a lumen of the second tube.

In accordance with a fifth aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,the membrane is selected from the group consisting of: a semipermeablemembrane, and a membrane including a plurality of perforations.

In accordance with a sixth aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,each electrode of the first electrode pair includes or is provided witha resistor.

In accordance with a seventh aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,at least one electrode of the second electrode pair includes or isprovided with a resistor.

In accordance with a eighth aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,the dialysis system includes an agitator in contact with at least one ofthe first and second chambers.

In accordance with a ninth aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,the dialysis system includes a control unit configured and arranged todetermine an amount of total chlorine in the at least partially purifiedwater sample via a signal obtained from the second electrode pair.

In accordance with a tenth aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,the chlorine detection component is incorporated within the waterpurification machine and enables at least one filter of the waterpurification machine to be evaluated.

In accordance with an eleventh aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, the dialysis system includes a user interface configured andarranged to indicate at least one of (i) an alarm to a user if a levelof total chlorine in the at least partially purified water sampleexceeds a predetermined value or (ii) indicate a safe status to a userif the level of total chlorine in the at least partially purified watersample falls below a predetermined value.

In accordance with a twelfth aspect of the present disclosure, which canbe used with the eleventh aspect in combination with other aspect oraspects listed herein, the predetermined maximum acceptable totalchlorine value is between and including 0.1 ppm to 0.5 ppm.

In accordance with a thirteenth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, at least one of the first chamber, the iodide reservoir, or thereducing agent reservoir is provided in a replaceable cartridge orcassette form.

In accordance with a fourteenth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, the dialysis system includes a plurality of pumps and valvespositioned and arranged to meter preset amounts of the at leastpartially purified water sample and the iodide into the first chamberand the reducing agent into the second chamber.

In accordance with a fifteenth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, the dialysis system includes at least one pump and valvepositioned and arranged to pump deionized water into at least one of thefirst and second chambers.

In accordance with a sixteenth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, the dialysis system includes at least one pump and valvepositioned and arranged to pull fluid from at least one of the first andsecond chambers to drain.

In accordance with a seventeenth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, the dialysis system prepares dialysate using the water from thewater purification machine, and wherein information concerning the leveltotal chlorine is displayed on a user interface of the dialysis machine.

In accordance with a eighteenth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, the iodide includes potassium iodide.

In accordance with a nineteenth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, the reducing agent includes sodium sulfate.

In accordance with a twentieth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, a method of providing hemodialysis to a subject in need thereofincludes (i) providing a dialysis system as disclosed herein, whereinthe at least partially purified water sample is obtained from water forpreparing dialysate, (ii) determining a level of total chlorine in theat least partially purified water sample, (iii) alerting the user totake a corrective action if the level of total chlorine exceeds apredetermined level, and (iv) allowing the user to perform thehemodialysis treatment if the level of total chlorine is below thepredetermined level.

In accordance with a twenty-first aspect of the present disclosure,which can be used with the twentieth aspect in combination with anyother aspect or aspects listed herein, the alerting step furtherincludes preventing the user from performing the hemodialysis treatmentuntil a subsequent level of total chlorine in a subsequent at leastpartially purified water sample is below the predetermined level.

In accordance with a twenty-second aspect of the present disclosure,which can be used in combination with any other aspect or aspects listedherein, a method of determining an amount of total chlorine in an atleast partially purified water sample associated with renal failuretherapy includes (i) providing a water purification machine, (ii)providing a dialysis machine, said dialysis machine receiving purifiedwater from the water purification machine, and (iii) providing a totalchlorine detection system in fluid communication with the waterpurification machine and the dialysis machine, wherein the totalchloride detection system includes (a) a first electrode pair configuredto generate tri-iodide in the presence of iodide and a total chlorinecompound upon application of a first voltage, and (b) a second electrodepair in fluid communication with the first electrode pair, the secondelectrode pair configured to determine a current associated with thetri-iodide generated by the first electrode pair upon application of asecond voltage to the second electrode pair, (iv) providing an at leastpartially purified water sample, the at least partially purified watersample including an amount of total chlorine, (v) monitoring abackground current via a tri-iodide detection circuitry, the backgroundcurrent associated with an amount of tri-iodide present in the systembefore introduction of a water sample, (vi) metering an amount of the atleast partially purified water sample into the total chlorine detectionsystem, (vii) monitoring a baseline current via a tri-iodide detectioncircuitry, the baseline current associated with the amount of totalchlorine in the at least partially purified water sample, (viii)generating a first amount of tri-iodide from the at least partiallypurified water sample by application of a first voltage to the firstelectrode pair, (ix) monitoring a first current by application of asecond voltage to the second electrode pair, the first currentassociated with the sum of the amount of total chlorine and the firstamount of tri-iodide, (x) generating a second amount of tri-iodide fromthe at least partially purified water sample by application of a thirdvoltage to the first electrode pair, (xi) monitoring a second current byapplication of a fourth voltage to the second electrode pair, the secondcurrent associated with the sum of the amount of total chlorine and thefirst and second amounts of tri-iodide, (xii) optionally generating athird amount of tri-iodide from the at least partially purified watersample by application of a fifth voltage to the first electrode pair,(xiii) optionally monitoring a third current induced by application of asixth voltage to the second electrode pair, the third current associatedwith the sum of the amount of total chlorine and the first, second andthird amounts of tri-iodide, and (xiv) calculating the amount of totalchlorine in the at least partially purified water sample using thebaseline current, the background current, and at least one of the firstcurrent, the second current, and the optional third current.

In accordance with a twenty-third aspect of the present disclosure,which can be used in combination with any other aspect or aspects listedherein, a plurality of subsequent or sequential voltages applied to thetri-iodide generating circuit are the same or substantially the same.

In accordance with a twenty-fourth aspect of the present disclosure,which can be used in combination with any other aspect or aspects listedherein, a plurality of subsequent or sequential voltages applied to thetri-iodide detecting circuit are the same or substantially the same.

In accordance with a twenty-fifth aspect of the present disclosure,which can be used in combination with any other aspect or aspects listedherein, a method of determining an amount of total chlorine in an atleast partially purified water sample associated with renal failuretherapy includes (i) providing an at least partially purified watersample from a water purification machine, said water purificationmachine in fluid communication with a dialysis machine (ii) monitoring abackground current in the system, the background current associated withthe amount of any tri-iodide present in the system before introductionof the water sample, (iii) metering out an amount of the at leastpartially purified water sample, (iv) monitoring a baseline current inthe at least partially purified water sample by application of a firstvoltage to the at least partially purified water sample, the baselinecurrent corresponding to the amount of total chlorine in the watersample, (v) generating a first amount of tri-iodide from the at leastpartially purified water sample, (vi) monitoring a first currentassociated with the sum of the total chlorine and the first amount oftri-iodide, (vii) generating a second amount of tri-iodide from the atleast partially purified water sample, (viii) monitoring a secondcurrent associated with the sum of the total chlorine and the first andsecond amounts of tri-iodide, (ix) optionally generating a third amountof tri-iodide from the at least partially purified water sample, (x)optionally monitoring a third current associated with the sum of theamount of total chlorine and the first, second and optional thirdamounts of tri-iodide, and (xi) calculating the total chlorineconcentration in the at least partially purified water sample using thebackground current, the baseline current and at least two of the firstcurrent, the second current, and the third current.

In accordance with a twenty-fourth aspect of the present disclosure, anyof the structure and functionality illustrated or described inconnection with FIGS. 1 to 10 can be used in combination with otheraspect or aspects listed herein.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

What is claimed is:
 1. A dialysis system comprising: a water treatmentmachine producing at least partially purified water; a dialysis machinefor providing dialysis therapy to a patient using the at least partiallypurified water from the water treatment machine; and a chlorinedetection testing unit configured to determine an amount of totalchlorine in an at least partially purified water sample from the watertreatment machine, the chlorine detection testing unit including firstand second chambers, at least one of the first and second chambersconfigured to receive the at least partially purified water sample fromthe water purification machine, at least one voltage source configuredto apply a voltage within the first and second chambers, and a controlunit configured to (i) cause the at least one voltage source to applythe voltage within the first and second chambers to generate an amountof tri-iodide within the first or second chamber containing the at leastpartially purified water sample, and (ii) monitor a current associatedwith the amount of tri-iodide generated within the first or secondchamber.
 2. The system of claim 1, wherein the chlorine detectiontesting unit is configured to monitor a background current associatedwith an amount of tri-iodide in the system before introduction of the atleast partially purified water sample.
 3. The system of claim 1, whereinthe first chamber is configured to receive the at least partiallypurified water sample from the water purification machine, and thesecond chamber is in fluid communication with a reducing agent reservoirconfigured to store a reducing agent that promotes generating tri-iodidefrom the at least partially purified water sample.
 4. The system ofclaim 1, wherein the chlorine detection testing unit includes: an iodidereservoir configured to store iodide fluid, and a reducing agentreservoir configured to store a reducing agent, wherein the firstchamber is in fluid communication with the iodide reservoir and thewater treatment machine, the second chamber is in fluid communicationwith the reducing agent reservoir, and the first and second chambers areseparated by a membrane that allows an electrical charge but not fluidto pass between the chambers, wherein the at least one voltage sourceincludes a first electrode pair and a second electrode pair, wherein oneelectrode of the first electrode pair is in electrical contact with aninterior of the first chamber and the other electrode of the firstelectrode pair is in electrical contact with an interior of the secondchamber, and wherein both electrodes of the second electrode pair are inelectrical contact with an interior of the first chamber.
 5. The systemof claim 4, wherein at least one of the electrodes includes carbonand/or a conductive metal.
 6. The system of claim 4, wherein at leastone of the first and second chambers includes a tube.
 7. The system ofclaim 4, wherein the first and second chambers both include tubes, andwherein the first chamber is disposed within a lumen of the second tube.8. The system of claim 4, wherein the membrane is a semipermeablemembrane.
 9. The system of claim 8, wherein the membrane includes aplurality of perforations.
 10. The system of claim 4, wherein eachelectrode of the first electrode pair comprises a resistor.
 11. Thesystem of claim 4, wherein at least one electrode of the secondelectrode pair comprises a resistor.
 12. The system of claim 4comprising an agitator, baffle, stirrer, or vibration mechanism incontact with at least one of the first and second chambers to mix fluidin the first and/or second chamber.
 13. The system of claim 4 which isconfigured to determine an amount of total chlorine in the at leastpartially purified water sample via a signal obtained from the secondelectrode pair.
 14. The system of claim 4, wherein at least one of thefirst chamber, the iodide reservoir, or the reducing agent reservoir isin a replaceable cartridge or cassette form.
 15. The system of claim 4comprising a plurality of pumps and valves configured to meter presetamounts of the at least partially purified water sample and the iodideinto the first chamber and the reducing agent into the second chamber.16. The system of claim 4 comprising at least one pump and valveconfigured to pump deionized water into at least one of the first andsecond chambers.
 17. The system of claim 4 comprising at least one pumpand valve configured to pull fluid from at least one of the first andsecond chambers to drain.
 18. The system of claim 1, wherein thechlorine detection testing unit is incorporated within the watertreatment machine and configured to evaluate at least one filter of thewater treatment machine.
 19. The system of claim 1 comprising a userinterface configured to indicate at least one of (i) an alarm to a userif a level of total chlorine in the at least partially purified watersample exceeds a predetermined value and (ii) a safe status to a user ifthe level of total chlorine in the at least partially purified watersample falls below a predetermined value.
 20. The system of claim 19,wherein the predetermined value is a value within a range between andincluding 0.01 ppm to 0.5 ppm.